Serial consistency configuration

Serial consistency levels in Hyper-Converged Database (HCD) control lightweight transaction isolation. The consistency levels for lightweight transactions are shown in the following table:

Level Description Usage

Level	Description	Usage
`SERIAL`	Achieves linearizable consistency for lightweight transactions by preventing unconditional updates.	This consistency level is for use only with lightweight transactions. Equivalent to How `QUORUM` is calculated. The `SERIAL` consistency level defines the serial consistency level for the Paxos consensus of lightweight transactions. The learn phase uses a normal consistency level to define which read operations will be guaranteed to complete immediately if lightweight writes are occurring. The `SERIAL` consistency level is ignored for any query that is not a conditional update.
`LOCAL_SERIAL`	Same as `SERIAL` but confined to a single datacenter. A conditional write must be written to the commit log and memtable on a quorum of replica nodes in the same datacenter.	Same as `SERIAL` but used to maintain consistency locally (within the single local datacenter). Equivalent to `LOCAL_QUORUM`.

SERIAL

Achieves linearizable consistency for lightweight transactions by preventing unconditional updates.

This consistency level is for use only with lightweight transactions. Equivalent to How QUORUM is calculated.

The SERIAL consistency level defines the serial consistency level for the Paxos consensus of lightweight transactions.

The learn phase uses a normal consistency level to define which read operations will be guaranteed to complete immediately if lightweight writes are occurring.

The SERIAL consistency level is ignored for any query that is not a conditional update.

LOCAL_SERIAL

Same as SERIAL but confined to a single datacenter. A conditional write must be written to the commit log and memtable on a quorum of replica nodes in the same datacenter.

Same as SERIAL but used to maintain consistency locally (within the single local datacenter). Equivalent to LOCAL_QUORUM.

For local consistency, which enforces serialization within the local datacenter, use:

LOCAL_SERIAL for LWT reads.
LOCAL_QUORUM and LOCAL_SERIAL for LWT writes.

For global consistency, which enforces serialization across multiple datacenters, use:

SERIAL for LWT reads.
QUORUM and SERIAL for LWT writes.

Serial consistency configuration

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